Hakea drupacea = H. suaveolens
Heide-Jørgensen H S. 1978. The xeromorphic leaves of Hakea
suaveolens R.Br. II. Structure of epidermal cells, cuticle development
and ectodesmata. - Bot. Tidsskr. 72: 227-244.
Epidermal ultrastructure and cuticle development were investigated
in leaves of the xeromorphic Australian shrub, Hakea suaveolens.
The heavily cutinized outer epidermal wall consists of seven distinct
layers. The cuticle proper is an up to 1.5µ thick zone of alternating
electron dense and translucent lamellae. The distinctness of the individual
lamellae is related to their ontogeny and probably to their synthetic
activity. The lamellae are believed to be involved in synthesis of epicuticular
wax. A reticulate cuticular layer starts to develop before expansion
has ceased. The production in spherosomes and transport through the
walls of wax- and cutin precursors are shown at different stages. Vesicles
containing fibrillar material are seen discharging their content to
the wall. Short, 50 nm thick membrane tubuli are found outside the plasmalemma.
Ectodesmata are demonstrated after Gilson fixation as well as after
glutaraldehyde/osmium tetroxide fixation. They proved to be extensions
of the innermost wall layer having a high content of pectins. Epidermal
structure is discussed in relation to the concept of xeromorphy.
According to Flora of Australia, Hakea suaveolens R. Br.
is now named Hakea drupacea (C. F. Gaertn.) Roem. & Schult.
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